What was the name of the scientist that studied experimentor bias?

There was a scientist who proved that the bias of the experimentor had a direct effect on the results of an experiment. He did this by placing before his subjects a frame that was designed to have a ball baring put in the top. The ball baring would then either pop to the left or to the right. After that, the ball baring fell to a second junction where again it could go left or right. If it went right first time and left second or vica versa it would be beneath the entrance hole.





This structructure carried on in this way forming a triangle. The ball barings were more likely to end up in the centre than they were to end up at the edge.





The scientist whos name eludes me asked his subjects to 'will' the ball barings one way. He would then ascertain through probability theory whether the ball barings had, in fact, skewed.





Remarkably, he found that they had. And when he asked his subjects to will them the other way they did.





Sound familiar? What was his name?

What was the name of the scientist that studied experimentor bias?
Could have not been a very famous scientist if people can't recall his/her name!